The New York Times alleged Tuesday that IAAF offcials "had evidence" against Schwazer "but made no effort to prevent him from competing in last summer's Olympic Games in London".

"The IAAF is aware of and shocked by the accusations made against it in today's New York Times concerning the ongoing investigation in Italy regarding the case of the sanctioned Italian race walker Alex Schwazer," the IAAF said in a statement.

"The IAAF categorically refutes these claims in the strongest possible terms.

"The case outlined involved abnormal blood results with respect to an Athletes Biological Passport and was handled in strict accordance with IAAF rules and those of WADA (World Anti-Doping Agency)."

The New York Times said the revelation had "stemmed from an investigation being conducted by prosecutors in Bolzano, Italy, into Dr Giuseppe Fischetto, the medical director for the Italian track and field federation and a member of the international track organisation's Anti-Doping Commission".

The report claimed that authorities had "obtained e-mail messages indicating that as early as April 2012, officials for track and field's world governing body, known as the IAAF, were aware of abnormal doping test results for the racewalker Alex Schwazer, who won gold at the 2008 Beijing Games".

Schwazer eventually failed a doping test conducted by WADA while he was training for the London Olympics.

The Italian anti-doping court banned him for three and a half years for testing positive for the blood booster EPO (erythropoietin), and he was removed from Italy's team before he had the chance to defend his Olympic 50km title.

The New York Times said that Italy's paramilitary police force, the Carabinieri, had this week "searched the home and office of Fischetto, as well as those of two other officials of the Italian track and field federation in Rome. They are accused of covering up the doping practices of Schwazer".